The present invention relates to a soluble form of intercellular adhesion molecule (sICAM-1) as well as the DNA sequence encoding sICAM-1. sICAM-1 and ICAM-1 have substantial similarity, in that they share the first 442 NH.sub.2 -terminal amino acids of the extracellular domain. However, sICAM-1 differs from ICAM-1 at the C-terminus, and these changes confer solubility to sICAM-1. ICAM-1 is known to mediate adhesion of many cell types, including endothelial cells, to lymphocytes which express lymphocyte function-associated antigen-1 (LFA-1). ICAM-1 has the property of directly binding LFA-1. There is also evidence for LFA-1 mediated adhesion which is not via ICAM-1. Additionally, ICAM-1 has the ability to bind both LFA-1 and human rhinovirus. It has the property of inhibiting infection of rhinovirus and Coxsackie A viruses. It may be used to antagonize adhesion of cells mediated by ICAM-1 binding including ICAM-1/LFA-1 binding and thus be useful in treatment of inflammation, graft rejection, LFA-1 expressing tumors, and other processes involving cell adhesion. Based on the substantial similarity of the extracellular domains of ICAM-1 and sICAM-1, sICAM-1 has the properties identified for ICAM-1.
The major Human Rhinovirus Receptor (HRR) has been transfected, identified, purified and reconstituted as described in co-pending U.S. patent applications Ser. Nos. 262570 and 262428 filed Oct. 25, 1988. This receptor has been shown to be identical to a previously described cell surface protein, ICAM-1. European Patent Application 0 289 949 describes a membrane associated cell adhesion molecule (ICAM-1) which mediates attachment of many cell types including endothelial cells to lymphocytes which contain LFA-1. This patent application provides a discussion of the present research in the field of intercellular adhesion molecules. It is important to note that the inventors specifically looked for an alternatively spliced mRNA for ICAM-1 and did not identify one. ICAM-1 was first identified based on its role in adhesion of leukocytes to T-cells (Rothlein, R. et a, J. Immunol. 137:1270-1274(1986)) which has been shown to be mediated by the heterotypic binding of ICAM-1 to LFA-1 (Marlin et al, Cell 51:813-819(1987)). The primary structure of ICAM-1 has revealed that it is homologous to the cellular adhesion molecules Neural Cell Adhesion Molecule (NCAM) and Mylein-Associated Glycoprotein (MAG), and has led to the proposal that it is a member of the immunoglobulin supergene family (Simmons et al, Nature 331:624-627 (1988); Staunton et al, Cell 52:925-933(1988)). The DNA sequence of cDNA clones are described in the above referenced papers by Simmons et al and Staunton et al, supra, from which the amino acid sequence of ICAM-1 can be deduced. The ICAM-1 molecule has a typical hydrophobic membrane spanning region containing 24 amino acids and a short cytoplasmic tail containing 28 amino acids. The ICAM-1 of the prior art is an insoluble molecule which is solubilized from cell membranes by lysing the cells in a non-ionic detergent. The solubilized ICAM-1 mixture in detergent is then passed through a column matrix material and then through a monoclonal antibody column matrix for purification.